1. FIELD OF THE INVENTION
The field of the invention is devices which prevent a bicycle from jackknifing by restricting the turning of the front wheel fork in order that the front wheel will never be permitted to be at right angles to the direction of travel of the bicycle.
2. DESCRIPTION OF THE RELATED ART
As every person who has ridden a bicycle no doubt knows, if the front wheel strikes an obstruction as the bicycle progresses forward, there is a tendency for the wheel to veer to the left or to the right. If unchecked, either by the bicycle rider firmly holding the handle bars or some other restraining device, the bicycle wheel will turn left or right until it has reached a position at right angles to the direction of travel. At that point, the front wheel now acts as a brake, not being able to roll over the obstruction and the bicycle stops forward travel completely and flips over the point of the wheel engaging the obstruction and throws the rider over the handle bars, the bicycle following.
The front wheel fork of a bicycle bows frontwards to make steering easier. This front bow is called a "negative caster". However, one result of this negative caster is that when the front wheel of the bicycle strikes an obstruction in the roadway, the tendency is to cause the bicycle wheel to turn either to the left or to the right and continue turning unless interrupted as above described.
This problem is not a recent problem and over the years there has been a number of devices constructed and patented which tend to present solutions to the problem above discussed, however, all devices known to the Inventor are rather complicated devices or provide a constant restraint upon the directional turning of the front wheel such as to interfere with the normal operator directed steering.
For example, Schriver in U.S. Pat. No. 1,230,801, and Parker in U.S. Pat. No. 4,006,915, disclose devices which attach springs to the front wheel fork prongs to place a constant restraint upon the turning of the fork in either direction. Each spring attaches to each prong with the springs converging to join to the bicycle frame lower cross bar. In an alternate embodiment, the two springs formerly attached to the front fork prongs are attached to the handle bars on either side of the front wheel fork shaft or post.
Christiansen in U.S. Pat. No. 691,597, discloses a device wherein a portion of the front wheel fork shaft above the fork bearing tube is made in the shape of a tear (in cross-sectional view) with spring loaded lever arms engaging opposite sides of the tear such that when the front fork turns, one lever arm is cammed out, the lever arm thus putting more pressure to return the fork to a position of least amount exerted pressure, i.e., return the fork to a forward direction.
Foehl, in U.S. Pat. No. 576,566, attaches a semicircular rod at its open points to opposite prongs in the front wheel fork and then permits the semicircular rod to slide through an eyelet mounted to the bicycle frame lower cross bar. At the center part of the semicircular curved rod is formed a notch and a spring loaded dog attached to the eyelet engages that notch such that to turn the bicycle front wheel fork left or right, the operator must overcome the spring loaded dog engaging the notch in the semicircular rod.
A rather interesting device for keeping the front wheel fork aligned straight ahead even when hitting obstructions is shown in the patent to Smith, U.S. Pat. No. 642,296. Smith corrects the problem of the negative caster by placing the front wheel fork turning axis ahead of the rotational point of the front wheel. This is accomplished by holding the steering wheel fork post at the end of a rotating bar, the rotating bar having its point of rotation along the previously mentioned axis which is ahead of the front wheel pivot point. Smith's device suffers from complexity and a great cost to manufacture and raises questions about whether the resultant strength of the bicycle frame after the improvement is added has been compromised.
While all the above devices do tend to restrict the turning of the bicycle steering wheel fork yet they are rather complex and expensive devices to construct and do impede steering of the bicycle during normal usage.
Accordingly, it would be useful to have a device adapted to interrupt the front wheel fork from turning to the point to where the bicycle is caused to jackknife but does not interfere with steering of the bicycle during normal riding. In addition, it would be useful if such a device may be easily installed and easily removed from the bicycle.